Section B? Guaranteed Piliavin, Rodin & Piliavin. It's the only study that hasn't come up in Section B since something like January 2009?
On that logic, I'd make a safe guess that the theme for the three studies will be field experiments, so that means Griffiths and Reicher & Haslam are likely to come up too. Best not to play with fire though - learn all the studies just to be sure.
As for Section C... well, the Behaviourist Perspective is a bona-fide contender. It hasn't appeared since January 2010 and is the only approach/perspective that hasn't come up twice since the new syllabus. You can bank on OCR picking another approach from recent papers just to throw candidates off the scent, so I'm putting extra effort into Developmental and Social psychology. But again - revise them all, as OCR could be expecting students to be expecting Behaviourism and may just be super ********s and not even ask about that.